Electromagnetic waves have been used in various applications to supply energy to objects. In the case of radio frequency (RF) radiation for example, electromagnetic energy may be supplied using a magnetron, which is typically tuned to a single frequency for supplying electromagnetic energy only in that frequency. One example of a commonly used device for supplying electromagnetic energy is a microwave oven. Many microwave ovens supply electromagnetic energy at or about a single frequency of 2.45 GHz.
Microwave oven user interfaces may include a keypad having several keys that indicate several options from which the user can select desired processing instructions, e.g., cooking time and cooking power level. Some keys indicate preprogrammed options such as thawing, warming prepared food, making popcorn, etc. Some user interfaces have display screens that display to the user the various options for cooking or processing the food and allow a user to indicate a desired instruction by touching the screen.